AM26LV31: Driving strength of AM26LV31IDR

Hi Karthik,

The cable length that can be supported in a given application depends on the transmitter's output amplitude (minimum output level), the cable loss characteristics, and the receiver's sensitivity (minimum required input level). The AM26LV31 will output a differential signal of at least 0.95 V when a 100-Ohm load is used between the two halves of the differential line (e.g., for end-of-line termination). Usually RS-422 receivers require differential input signal amplitudes of at least 0.2 V, and you may choose to have a certain amount of margin above this in order to ensure robust communication. The difference between the transmitter output amplitude and the receiver input amplitude gives you the amount of loss that can be budgeted in the cable. Note that at higher signaling rates this becomes more complex, since you need to also consider how high-frequency losses may not just decrease the overall signal amplitude but also distort the timing and introduce jitter. Here is an application note that goes into more detail on these concerns (on RS-485 specifically, but the same concerns will apply to RS-422 as well):

www.ti.com/.../slla375.pdf

Max